<?php

namespace Controllers;

class Post
{
    public function index($page = '1')
    {
        $db = db();
        $offset = ($page >= 1) ? ($page - 1) : 0;
        $offset *= 10;
        $sql = 'SELECT * FROM posts ORDER BY create_at DESC LIMIT ?,10';
        $query = $db->prepare($sql);
        $query->bindValue(1, $offset, \PDO::PARAM_INT);
        $query->execute();
        $posts = $query->fetchAll(\PDO::FETCH_CLASS, 'Core\\Record');
        $offset += 10;
        $query->bindValue(1, $offset, \PDO::PARAM_INT);
        $query->execute();
        $next = $query->fetchAll(\PDO::FETCH_CLASS, 'Core\\Record');
        $sql = 'SELECT id, keyword, COUNT(id) AS num_of_posts FROM ('.
               'tags JOIN post_tag ON id=tag_id) GROUP BY id ORDER BY keyword';
        $query = $db->prepare($sql);
        $query->execute();
        $tags = $query->fetchAll(\PDO::FETCH_CLASS, 'Core\\Record');
        $is_last = count($next) == 0 ? true : false;
        return view('post.index', [
            'posts' => $posts,
            'tags' => $tags,
            'page' => $page,
            'is_last' => $is_last,
            'pager_uri' => ''
        ]);
    }

    public function showCreate()
    {
        return view('post.create', [
            'title' => '',
            'content' => '',
            'tags' => ''
        ]);
    }

    public function show($id)
    {
        $post = $this->getPost($id);
        if ($post != null) {
            return view('post.show', [
                'post' => $post,
                'tags' => $this->getTags($id),
                'comments' => $this->getComments($id)
            ]);
        }
        throw new \Phroute\Phroute\Exception\HttpRouteNotFoundException;
    }

    public function showUpdate($id)
    {
        if (! $this->isAuthor($id)) {
            header('HTTP/1.0 403 Forbidden');
            die();
            return false;
        }
        if ($post = $this->getPostWithTags($id)) {
            return view('post.edit', ['post' => $post]);
        }
        throw new \Phroute\Phroute\Exception\HttpRouteNotFoundException;
    }

    public function create()
    {
        if (! $this->titleValid()) {
            header('Location: /post/create');
            return false;
        }
        $id = $this->setPost();
        $tags = array_values(array_filter(
            array_map('trim', explode(',', $_POST['tags']))
        ));
        $this->setTags($tags);
        $this->syncPostTag($id, $tags);
        header("Location: /post/$id");
        return false;
    }

    public function update($id)
    {
        if (! $this->isAuthor($id)) {
            header('HTTP/1.0 403 Forbidden');
            die();
            return false;
        }
        if (! $this->titleValid()) {
            header("Location: /post/$id/edit");
            return false;
        }
        $this->updatePost($id);
        $tags = array_values(array_filter(
            array_map('trim', explode(',', $_POST['tags']))
        ));
        $this->setTags($tags);
        $this->syncPostTag($id, $tags);
        header("Location: /post/$id");
        return false;
    }

    public function delete($id)
    {
        if (! $this->isAuthor($id)) {
            header('HTTP/1.0 403 Forbidden');
            die();
            return false;
        }
        $sql = 'DELETE FROM posts WHERE id=?';
        $query = db()->prepare($sql);
        $query->execute([$id]);
        $path = parse_url($_SERVER['HTTP_REFERER'])['path'];
        if (preg_match('/^\/post\//', $path)) {
            header('Location: /');
            return false;
        }
        header("Location: $path");
        return false;
    }

    private function isAuthor($id)
    {
        $sql = 'SELECT author FROM posts WHERE id=?';
        $query = db()->prepare($sql);
        $query->execute([$id]);
        $post = $query->fetchAll(\PDO::FETCH_CLASS, 'Core\\Record');
        return (count($post) != 0 &&
                $post[0]->author == $_SESSION['username']);
    }

    private function titleValid()
    {
        if (empty(trim($_POST['title']))) {
            $_SESSION['errors'] = ['Post title cannot be empty.'];
            $_SESSION['inputs'] = [
                'title' => $_POST['title'],
                'content' => $_POST['content'],
                'tags' => $_POST['tags']
            ];
            return false;
        }
        return true;
    }

    private function getPost($id)
    {
        $sql = 'SELECT p.*, COUNT(c.id) AS num_of_comments FROM posts AS p ' .
               'LEFT JOIN comments AS c ON p.id=c.comment_to WHERE p.id=:id';
        $query = db()->prepare($sql);
        $query->bindValue(':id', $id, \PDO::PARAM_INT);
        $query->execute();
        $post = $query->fetchAll(\PDO::FETCH_CLASS, 'Core\\Record');
        if (count($post) != 0) {
            return $post[0];
        }
        return null;
    }

    private function getTags($id)
    {
        $sql = 'SELECT * FROM tags WHERE id IN ( ' .
               "SELECT tag_id FROM post_tag WHERE post_id=? ) ORDER BY keyword";
        $query = db()->prepare($sql);
        $query->execute([$id]);
        return $query->fetchAll(\PDO::FETCH_CLASS, 'Core\\Record');
    }

    private function getComments($id)
    {
        $sql = 'SELECT c.*, u.email FROM comments AS c, users AS u ' .
               'WHERE c.comment_to=? AND c.author=u.name ORDER BY c.create_at';
        $query = db()->prepare($sql);
        $query->execute([$id]);
        return $query->fetchAll(\PDO::FETCH_CLASS, 'Core\\Record');
    }

    private function getPostWithTags($id)
    {
        $sql = "SELECT p.*, GROUP_CONCAT(DISTINCT t.keyword SEPARATOR ', ') AS tags " .
               'FROM posts AS p, tags AS t WHERE p.id=:id AND t.id IN ( ' .
               'SELECT tag_id FROM post_tag WHERE post_id=:id ) ORDER BY t.keyword';
        $query = db()->prepare($sql);
        $query->bindValue(':id', $id, \PDO::PARAM_INT);
        $query->execute();
        $post = $query->fetchAll(\PDO::FETCH_CLASS, 'Core\\Record');
        if (count($post) != 0) {
            return $post[0];
        }
        return null;
    }

    private function setPost()
    {
        $db = db();
        $sql = 'INSERT INTO posts VALUES (NULL, ?, ?, ?, DEFAULT, DEFAULT)';
        $query = $db->prepare($sql);
        $query->execute([
            trim($_POST['title']),
            trim($_POST['content']),
            $_SESSION['username']
        ]);
        return $db->lastInsertId();
    }

    private function updatePost($id)
    {
        $sql = 'UPDATE posts SET title=?, content=? WHERE id=?';
        $query = db()->prepare($sql);
        $query->execute([
            trim($_POST['title']),
            trim($_POST['content']),
            $id
        ]);
    }

    private function setTags($tags)
    {
        if (count($tags) != 0) {
            $rows = [];
            foreach ($tags as $tag) {
                array_push($rows, "(NULL, ?)");
            }
            $sql = 'INSERT INTO tags VALUES ' . implode(', ', $rows) .
                   ' ON DUPLICATE KEY UPDATE keyword=keyword';
            $query = db()->prepare($sql);
            $query->execute($tags);
        }
    }

    private function syncPostTag($post_id, $tags)
    {
        $db = db();
        if (count($tags) != 0) {
            $tuple_holders = [];
            $element_holders = [];
            $rows = [];
            $tag_ids = $this->tagsToIds($tags);
            foreach ($tag_ids as $tag_id) {
                array_push($tuple_holders, '(?, ?)');
                array_push($element_holders, '?');
                array_push($rows, $post_id, $tag_id);
            }
            $sql = 'INSERT INTO post_tag VALUES ' . implode(', ', $tuple_holders) .
                   ' ON DUPLICATE KEY UPDATE post_id=post_id';
            $query = $db->prepare($sql);
            $query->execute($rows);
            $sql = 'DELETE FROM post_tag WHERE post_id=? AND tag_id NOT IN ' .
                   '(' . implode(', ', $element_holders) . ')';
            $query = $db->prepare($sql);
            $query->bindValue(1, $post_id, \PDO::PARAM_INT);
            foreach ($tag_ids as $index => $tag_id) {
                $query->bindValue($index + 2, $tag_id, \PDO::PARAM_INT);
            }
            $query->execute();
        } else {
            $sql = 'DELETE FROM post_tag WHERE post_id=?';
            $query = $db->prepare($sql);
            $query->execute([$post_id]);
        }
    }

    private function tagsToIds($tags)
    {
        $element_holders = [];
        foreach ($tags as $tag) {
            array_push($element_holders, '?');
        }
        $sql = 'SELECT DISTINCT id FROM tags WHERE keyword IN ' .
               '(' . implode(', ', $element_holders) . ') ORDER BY id';
        $query = db()->prepare($sql);
        $query->execute($tags);
        return $query->fetchAll(\PDO::FETCH_COLUMN, 0);
    }
}